999718921 has 2 divisors, whose sum is σ = 999718922. Its totient is φ = 999718920.

The previous prime is 999718883. The next prime is 999718931. The reversal of 999718921 is 129817999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 564537600 + 435181321 = 23760^2 + 20861^2 .

It is an emirp because it is prime and its reverse (129817999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 999718921 - 2⁹ = 999718409 is a prime.

It is not a weakly prime, because it can be changed into another prime (999718931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499859460 + 499859461.

It is an arithmetic number, because the mean of its divisors is an integer number (499859461).

Almost surely, 2^999718921 is an apocalyptic number.

It is an amenable number.

999718921 is a deficient number, since it is larger than the sum of its proper divisors (1).

999718921 is an equidigital number, since it uses as much as digits as its factorization.

999718921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 734832, while the sum is 55.

The square root of 999718921 is about 31618.3320401314. The cubic root of 999718921 is about 999.9062982203.

The spelling of 999718921 in words is "nine hundred ninety-nine million, seven hundred eighteen thousand, nine hundred twenty-one".